A. Field of the Invention
The present invention relates to a modified maxadilan protein, a potent vasodilator peptide, and to a modified maxadilan fusion protein. This invention also relates to DNA sequences encoding modified maxadilan and modified maxadilan fusion proteins and vectors comprising these DNA sequences. The present invention further relates to a method of producing modified maxadilan having increased specific activity and to a method for increasing the yield of maxadilan protein produced using recombinant methods.
B. Description of the Prior Art
Maxadilan is a potent vasodilator peptide, which is present in the saliva of the sand fly Lutzomyia longipalpis. This sand fly spreads the disease leishmaniasis by secreting the protozoan parasite, Leishmania, into its victim when the sand fly probes for a blood meal. It is believed that the potent vasodilating effects of maxadilan enhance the infectivity of the parasite. Maxadilan is useful as a therapeutic agent, which can increase blood flow to defined areas in a patient's body.
In order to fully characterize the biological activity of maxadilan and to thoroughly investigate the therapeutic uses for this important protein, an adequate supply of maxadilan protein is essential. At present, maxadilan can be obtained by purification of salivary maxadilan from sand fly salivary glands or by recombinant DNA methods. Lerner et al. and Shoemaker have cloned and expressed the gene for maxadilan as a fusion protein with glutathione S-transferase (GST), a bacterial protein. Lerner et al., "Maxadilan: Cloning And Functional Expression Of A Gene Encoding This Potent Vasodilator Peptide," Journal of Biological Chemistry, Vol. 267, No. 2, pp. 1062-66, 1992.
The GST fusion protein is cleaved by Factor Xa to release maxadilan protein. Factor Xa is an expensive cleavage enzyme and does not cleave the maxadilan GST fusion protein as efficiently as desired. Because of the high cost and lower than desired cleavage efficiency of Factor Xa, there exists a need in the art for large quantities of recombinant maxadilan that can be produced less expensively and more efficiently.